EXPLANATION OF PLATE 47. 81 



Fig. 6. BodyofActinocrinitesSO-dactylus (NaveEncrinite 

 of Parkinson) copied from Miller's Crinoidea, P. 98. 

 PI. 11. (See V. I. p. 429. Note.) 



Q. Pectoral Plates. 



R. Capital Plates. 



X. Orifice of the Mouth, or Proboscis, capable of elon- 

 gation for sucking in food. 



Fig. 7. Another Body of a Nave Encrinite, drawn by Mr 

 J. Sowerby from a specimen in the British Museum. 

 The same is Figured by Parkinson, in his Organic 

 Remains, Vol. II. PL XVII. Fig. 3. The lateral pro- 

 jections are the commencement of the side arms. 

 This specimen has been corroded with acid, and con- 

 sequently has lost the superficial Corrugations and 



in his admirahle Monograph on Crinoidea, p. 97. "The mechanism 

 of the joints of the side arms, where these insert into the column, is 

 well worthy of notice, particularly in old specimens. In the earlier 

 stage of their formation, the side arms being very short, and liaving 

 then little weight, a less firm mode of adhesion to the column than 

 becomes requisite at a subsequent period, being then sufficient, we 

 do not find more than one joint lodged in a socket, or concave im- 

 pression on the column ; but when increase of size renders a stronger 

 support necessary, two or three succeeding joints of the side arms 

 become imbedded in this socket, (for which its extension as already 

 noticed allows room) and these joints instead of being arranged in a 

 series branching off at right angles from the column, become oblique, 

 their direction inclining upwards, so as to aid in bearing the addi- 

 tional weight. The first joint of the side arms, where thus obliquely 

 inserted in the columnar socket, have that portion of their circum- 

 ference which is presented towards the upper part of the column, 

 truncated, in such a curve as may fit them to the concavity of the 

 impression where they rest against it. 



The surface of these joints, which fit into the columnar impression, 

 is smooth, being destined for adhesion only, but the articulating sur- 

 face between the contiguous joints, where motion also is to be allowed, 

 exhibits the usual mechanism of radiated ridges and furrows. These 

 joints are convex on the side nearest the column, and concave on that 

 most remote." 



GEOL. II. G 



